This invention relates to polymer polyols that are the free-radical polymerization product of a base polyol, at least one ethylenically unsaturated monomer, and optionally, a preformed stabilizer, in the presence of at least one free-radical polymerization initiator and at least one chain transfer agent, in which the base polyol is comprised of a natural oil. A process for preparing these polymer polyols is also described. The present invention also relates to a polyurethane foam prepared from these polymer polyols and to a process for the preparation of these polyurethane foams.
U.S. Pat. No. 5,854,358 describes the polymerization of monomers in the presence of a polyol and a castor oil-polyol product. More specifically, this reference describes stable, low viscosity, graft copolymer dispersions prepared by free-radically polymerizing a reaction mixture comprising one or more olefinic monomers, one or more basic polyols and one or more hydroxyl compounds which are modified with castor oil, in the presence of a free-radical catalyst. These hydroxyl compounds modified with castor oil have molecular weights of 6000 to 100,000 g/mole and functionalities of 2 to 6 and are prepared from an excess of castor oil with a polyol such that the molar ratio of castor oil to hydroxyl group containing compounds is 1.1:1 to 10:1. The use of an excess of castor oil gives active modified hydroxyl compounds. The molecular weights of these modified hydroxyl compounds can be increased by adding one or more carboxylic acids which are at least difunctional, or one or more carboxylic acids derivatives during the modification reaction to give molecular weights of 7000 to 100,000 g/mol.
WO 2006/065345 also discloses polymer polyols and polymer dispersions prepared from vegetable-oil based hydroxyl-containing materials. These polymer polyols have a polyol continuous phase and dispersed polymer particles, in which the polyol continuous phase includes at least one hydroxymethyl-containing polyester polyol which is derived from a fatty acid or a fatty acid ester. In particular, these hydroxymethyl-containing polyester polyols are prepared by reacting a hydroxymethyl group-containing fatty acid having from 12 to 26 carbon atoms, or an ester thereof, with an alcohol or amine initiator compound having an average of at least one hydroxyl or primary/second amine group per molecule. The resultant hydroxymethyl polyester polyol contains an average of at least 1.3 repeating units derived from hydroxymethyl-group-containing fatty acid or ester per total number of hydroxyl, primary/secondary amine groups in the initiator compound and has an equivalent weight of at least 400 to 15,000.
Advantages of the present invention include an efficient process for producing stable and low viscosity polymer polyols with a high renewable content that can be substituted for largely petrochemical based polymer polyols in the manufacture of high quality urethane foams. This substitution can help to conserve scarce petroleum reserves and offers other environmental benefits such as lower energy usage and reduced carbon dioxide emissions. These natural oil based polymer polyols provide another means for raising the renewable content of flexible and semirigid polyurethane foams beyond what would be possible through the use of only renewable base polyols. This would be particularly advantageous for incorporating more renewable content into higher firmness foams that are typically produced with high levels of polymer polyols and low amounts of base polyols.